(function(win, doc) {
	//浏览器缩放时
	win.onresize = function() {
		change();
	};
	change();
	function change() {
		var oFs = doc.documentElement.clientWidth / (640/ 20);
			//设置根目录字体大小
			doc.documentElement.style.fontSize = oFs + 'px';
		}
})(window, document);
